Jquery Calculator help

So I’ve got this nifty little jquery calculator thing and I really need it to return a number so that can be passed on. Right now, it adds fine but Im not able to retrieve the info to pass to the form it belongs to.

The script…

$(document).ready(
		function (){
			// update the plug-in version
			$("#idPluginVersion").text($.Calculation.version);
			
			// bind the recalc function to the quantity fields
			$("input[name^=qty_item_]").bind("keyup", recalc);
			// run the calculation function now
			recalc();

			// automatically update the "#totalSum" field every time
			// the values are changes via the keyup event
			$("input[name^=sum]").sum("keyup", "#totalSum");
			
			// automatically update the "#totalAvg" field every time
			// the values are changes via the keyup event
			$("input[name^=avg]").avg({
				bind:"keyup"
				, selector: "#totalAvg"
				
				// if an invalid character is found, change the background color
				, onParseError: function(){
					this.css("backgroundColor", "#cc0000")
				}
				// if the error has been cleared, reset the bgcolor
				, onParseClear: function (){
					this.css("backgroundColor", "");
				}
			});
			
			// automatically update the "#minNumber" field every time
			// the values are changes via the keyup event
			$("input[name^=max]").max("keyup", {
				selector: "#numberMax"
				, oncalc: function (value, options){
					// you can use this to format the value
					$(options.selector).val(value);
				}
			});

			// this calculates the sum for some text nodes
			$("#idTotalTextSum").click(
				function (){
					// get the sum of the elements
					var sum = $(".textSum").sum();

					// update the total
					$("#totalTextSum").text(sum);
				} 
			);

		
		}
	);
	
	function recalc(){
		$("[id^=total_item]").calc(
			// the equation to use for the calculation
			"qty * price",
			// define the variables used in the equation, these can be a jQuery object
			{
				qty: $("input[name^=qty_item_]"),
				price: $("[id^=price_item_]"),
				SF_Billing_GrandTotal: $("[id^=grandTotal]").text.value
			},
			// define the formatting callback, the results of the calculation are passed to this function
			function (s){
				// return the number as a dollar amount
				return "$" + s.toFixed(2);
			},
			// define the finish callback, this runs after the calculation has been complete
			function ($this){
				// sum the total of the $("[id^=total_item]") selector
				var sum = $this.sum();
				
				$("#grandTotal").text(
					// round the results to 2 digits
					"$" + sum.toFixed(2)
					
				); 
				SF_Billing_GrandTotal = eval(grandTotal.value);
			}
		);
	} 

The table…

<table width="500">
				<col style="width: 50px;" />
				<col />
				<col style="width: 60px;" />
				<col style="width: 110px;" />
				<tr>
					<th>
						Qty
					</th>
					<th align="left">
						Product
					</th>
					<th>
						Price
					</th>
					<th>
						Total
					</th>
				</tr>
				<tr>
					<td align="center">
						<input type="text" name="qty_item_1" id="qty_item_1" value="0" size="2" />
					</td>
					<td>
						Learning jQuery
					</td>
					<td align="center" id="price_item_1">
						$50.00
					</td>
					<td align="center" id="total_item_1">
						$0.00
					</td>
				</tr>
				<tr>
					<td align="center">
						<input type="text" name="qty_item_2" id="qty_item_2" value="0" size="2" />
					</td>
					<td>
						Framed Award
					</td>
					<td align="center" id="price_item_2">
						$250.00
					</td>
					<td align="center" id="total_item_2">
						$0.00
					</td>
				</tr>
        <tr>
          <td></td>
          <td>Total Amount :</td>
          <td></td>
    <td align="center" id="grandTotal" ><input type="hidden" id="SF_Billing_GrandTotal" value="0" /></td>
        </tr>
			</table>

The plugin can be found at http://www.pengoworks.com/workshop/jquery/calculation/jquery.calculation.js and http://www.pengoworks.com/workshop/jquery/field/jquery.field.js

essentially, I’m trying to populate the hidden input field with the grandTotal value. Any help would be awesome! thanks